The prior art discloses numerous types of thermal solar panels comprising an absorber containing heat-bearing fluid which may be water for example, water mixed with an antigel or even just air.
According to a first category of thermal solar panels illustrated in FIG. 1, these panels 1 comprise an absorber 2 formed by tubes 3 fitted with fins in which heat-bearing fluid circulates in closed circuit. The tubes are heated conventionally by solar radiation and transmit heat to the heat-bearing fluid which circulates inside these tubes. For a higher yield, the absorber is placed in a glazed insulating box, not illustrated here, to get a greenhouse effect. A reflector is usually arranged under the tubes to further boost heat recovery.
Another existing type of absorber comprises a metal plate arranged under the glass panel, and under which are arranged fine metal conduits containing heat-bearing fluid and winding over the entire length of the panel.
Such thermal solar panels have a number of drawbacks, including more especially the mechanical complexity and fragility of the absorber as well as a relatively low yield due to the low volume of heat-bearing fluid for a determined glazed surface of the solar panel.
According to a second category of thermal solar panels, known especially from document CH 624 753, the solar sensor 1, shown in FIG. 2, comprises two metallic plates 2, between which heat-bearing fluid circulates. Pads in the form of bosses 4 are foamed at regular intervals on the metal plates 2. The bosses of one metal plate are offset by a semi-boss relative to those of the other plate. The two metal plates 2 are welded together by means of welding beads 6 made by a roller and arranged so that a turbulent flow of the heat-bearing fluid circulating between the plates is generated. With such a solar sensor, a higher yield can be attained independently of the position of the sun. Also, the turbulent flow brings good heat exchange between the plates metal and heat-bearing fluid. Such a solar sensor can be made at less cost and be easily mounted on the exterior of a roof.
Even though the solar sensor presented within the scope of document CH 624 753 has a higher yield and is mechanically simpler than those comprising tubes, it still has some drawbacks, in particular resistance to pressure exerted by heat-bearing fluid on the metal plates of the sensor. In fact, it has been noted within the scope of the present invention that in normal usage conditions dilation of heat-bearing fluid contained in the sensor causes pressure on the plates, inducing the welding beads located between the bosses to give way.
Document WO 01/14080 in particular also discloses a heat exchanger 23, illustrated in FIGS. 3a and 3b, comprising two walls 13, 15 connected specifically by compression and forming into a plurality of points 11 then sealed at their edge 25. Although this type of alternative solution enables a stronger join of the two walls 13 and 15, it also means some drawbacks and in particular needs a relatively large flat space 19 around each connection point 11. The need for such space 19 makes it difficult to implement on a solar sensor structure such as presented in document CH 624 753. In fact, if the space between the bosses is increased, all the more reducing the communication surfaces between the bosses of the two plates and resulting in making the path of the heat-bearing fluid less efficient, then this space is kept as such and in this case the risk of perforation of a boss is considerably higher and the tightness of the sensor is threatened.